package org.top10.util;

//HTMLParser Library $Name: v1_5 $ - A java-based parser for HTML
//http://sourceforge.org/projects/htmlparser
//Copyright (C) 2004 Derrick Oswald
//
//Revision Control Information
//
//$Source: /cvsroot/htmlparser/htmlparser/src/org/htmlparser/util/sort/Ordered.java,v $
//$Author: derrickoswald $
//$Date: 2004/01/02 16:24:58 $
//$Revision: 1.11 $
//
//This library is free software; you can redistribute it and/or
//modify it under the terms of the GNU Lesser General Public
//License as published by the Free Software Foundation; either
//version 2.1 of the License, or (at your option) any later version.
//
//This library is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
//Lesser General Public License for more details.
//
//You should have received a copy of the GNU Lesser General Public
//License along with this library; if not, write to the Free Software
//Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//


/**
* Describes an object that knows about ordering.
* Implementors must have a comparison function,
* which imposes a partial ordering on some
* collection of objects. Ordered objects can be passed to a
* sort method (such as org.htmlparser.util.sort.Sort) to allow precise control
* over the sort order.
* <p>
* An set of elements S is partially ordered
* if and only if <code>e1.compare(e2)==0</code> implies that
* <code>e1.equals(e2)</code> for every e1 and e2 in S.
* <p>
* This all goes away in JDK 1.2.
* <p>
* For use with java.lang.Comparable from JDK 1.2:
* <pre>
* public int compare (Object o1, Object o2)
* {
*     return (((Ordered)o1).compare (o2));
* }
* </pre>
* @see Sort
*/
public interface Ordered
{
 /**
  * Compares this object with another for order.
  * Returns a negative integer, zero, or a positive integer
  * as this object is less than, equal to, or greater
  * than the second.
  * <p>
  * The implementor must ensure that
  * <code>sgn(x.compare(y)) == -sgn(y.compare(x))</code>
  * for all x and y. (This implies that <code>x.compare(y)</code>
  * must throw an exception if and only if <code>y.compare(x)</code>
  * throws an exception.)
  * <p>
  * The implementor must also ensure that the relation is transitive:
  * <code>((x.compare(y)>0) && (y.compare(z)>0))</code>
  * implies <code>x.compare(z)>0</code>.
  * <p>
  * Finally, the implementer must ensure that
  * <code>x.compare(y)==0</code> implies that
  * <code>sgn(x.compare(z))==sgn(y.compare(z))</code>
  * for all z.
  * @param that The object to compare this object against.
  * @return A negative integer, zero, or a positive
  * integer as this object is less than, equal to,
  * or greater than the second.
  * @exception ClassCastException The arguments type prevents it
  * from being compared by this Ordered.
  */
 public int compare (Object that);
}
